Predictive coding for compression of video signal functions best when current images are easily predicted from temporally adjacent images. However when the source images contain noise, accurate prediction becomes difficult and the compression efficiency declines or the reproduced image quality degrades or both. It is therefore desirable to minimize noise in the video signal to be compressed prior to the compression process.
Consider FIG. 1 which illustrates a prior art predictive image coding system. Elements 12-22 form the actual predictive coder which will be described herein after. Noise reduction, in such prior art systems typically include a recursive noise reduction filter 10 to preprocess the video signal prior to compression. Field or frame recursive filters tend to have been preferred because they can effectively reduce noise components within the bandwidth of the active signal. However, such filters are also very memory intensive and require relatively sophisticated processing circuitry in order to perform significant noise reduction without introducing undesirable artifacts around moving image features
It is an object of the present invention to provide a highly effective noise filter apparatus and method for predictive encoders with minimal additional hardware.